ORION TELESCOPES & BINOCULARS ShortTube 80 9386 User manual

IN 121 Rev. B 04/02
Providing Exceptional Consumer Optical Products Since 1975
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E-mail: [email protected]
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INSTRUCTION MANUAL
Orion®
ShortTube™ 80
80mm Rich-Field Refracting Telescope
#9386

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WARNING: Never look at the sun with your telescope
(or even with just your eyes) without a professionally
made solar filter. Permanent eye damage or blindness
could result. Young children should use this telescope
only with adult supervision.
Avoid using the type of solar filter that screws into an
eyepiece. They are susceptible to cracking under the
intense heat that builds up near the focus point, and
could cause severe retinal damage. Use only the type of
solar filter that covers the front of the telescope. Be sure
also to cover the front of the finder scope with aluminum
foil or another opaque material to prevent physical dam-
age to the internal components of the scope itself as well
as to your eyes.
Figure 1. The ShortTube 80 refractor
Eyepiece
45° Correct-
image
diagonal
1/4"-20
Mounting
block
Dew/Glare
shield
Correct-image
finder scope
Finder scope bracket
Focus lock
set-screw
Focus wheel
Dovetail
mount
Welcome to a new world of adventure! -Your Orion ShortTube 80 is a fine-quality instrument designed for both daytime ter-
restrial viewing and nighttime stargazing. Compact, portable, and easy to use, this versatile scope will provide many hours of
enjoyment for the whole family.
These instructions will help you set up and properly use and care for your telescope. Please read them over thoroughly before
getting started.
Parts List
Qty. Description
1 Optical tube assembly
1 25mm Sirius Plössl 1.25” eyepiece (16x)
1 10mm Sirius Plössl 1.25” eyepiece (40x)
1 45° correct-image diagonal, 1.25”
1 6x26 correct-image finder scope
1 Objective lens cap
1 Finderscope bracket with O-ring

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Getting Started
The ShortTube 80 comes nearly fully assembled from the
factory. The telescope’s optics have been installed and col-
limated, so you should not have to make any adjustments to
them. Open the box and inspect the contents to make sure
all of the items in the parts list are present.
Please keep the original shipping box. In the unlikely event
you should need to ship the telescope back to Orion for war-
ranty repair service, you should use the original packaging.
The box also makes a very good container for storing the
telescope when it is not in use.
Installing the Finder Scope
To place the finder scope in the finder scope bracket, first
unthread the two black nylon thumbscrews until the screw
ends are flush with the inside diameter of the bracket. Place
the O-ring that comes on the base of the bracket over the
body of the finder scope until it seats into the slot on the
middle of the finder scope. Slide the eyepiece end (nar-
row end) of the finder scope into the end of the bracket’s
cylinder opposite the adjustment screws while pulling the
chrome, spring-loaded tensioner on the bracket with your
fingers (Figure 2b.) Push the finder scope through the
bracket until the O-ring seats just inside the front opening
of the bracket’s cylinder. Now, release the tensioner and
tighten the two black nylon screws a couple of turns each to
secure the finder scope in place. Secure the bracket to the
dovetail mount on the optical tube with the knurled thumb-
screw provided.
Installing the Diagonal and Eyepiece
Insert the 45° diagonal into the focuser tube and secure with
the knurled thumbscrew. Then insert the 25mm Plössl eye-
piece into the 45° diagonal and secure it in place with the
thumbscrews on the diagonal. (Always loosen the thumb-
screws before rotating or removing the diagonal or an
eyepiece.)
Mounting the Telescope on a Tripod
The ShortTube 80 can be mounted on any standard cam-
era tripod that has a 1/4”-20 stud. The stud threads into the
small block on the underside of the telescope’s optical tube.
Alternatively, the telescope can be attached to an equatorial
mount equipped with a 1/4”-20 adapter. An equatorial mount
is desirable for astronomical viewing because it allows easy
manual tracking of celestial objects as the Earth rotates. Also,
the setting circles on the mount enable you to locate objects
by their celestial coordinates (right ascension and declination),
which can be found in many observing books and star atlases.
Focusing
The ShortTube 80mm is equipped with a precision rack-
and-pinion focuser. When you first look in the eyepiece, the
image you see may be fuzzy, or out of focus. If so, gently
turn one of the large focusing wheels with your fingers until
the image becomes sharp. You will have to readjust the
focus when aiming at subjects of varying distances, or after
changing eyepieces. Make sure the focus lock screw is loos-
ened before focusing. After focusing, you can tighten it to
lock the telescope’s focus into place.
Do You Wear Eyeglasses?
If you wear eyeglasses, you may be able to keep them on
while you observe, if your eyepieces have enough “eye
relief” to allow you to see the whole field of view. You can
find out by looking through the eyepiece first with your
glasses on and then with them off, and see if the glasses
restrict the view to only a portion of the full field. If they do,
you can easily observe with your glasses off by just refocus-
ing the telescope the needed amount.
Aligning the Finder Scope
The ShortTube 80 comes with a 6x26 correct-image achro-
matic finder scope. (The 6x means six-times magnification,
and the 26 indicates a 26mm aperture.) The finder scope
makes it easier to locate the subject you want to observe in
the telescope, because the finder scope has a much wider
Figure 2a The 6x26 correct-image finder scope and bracket
Focus
lock-ring
Alignment thumbscrews
Tensioner
Figure 2b. Inserting the finder scope into the finder scope bracket

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field of view. Unlike most finder scopes, images viewed in
the correct-image finder scope will appear properly oriented
(same as the naked eye), which makes finding objects even
easier.
Before you use the finder scope, it must be precisely aligned
with the telescope, so they both point to exactly the same
spot. Alignment is easiest to do in daylight, rather than at
night under the stars. First, insert the lowest-power (25mm)
eyepiece into the main telescope’s focuser. Then point the
telescope at a discrete object such as the top of a telephone
pole or a street sign that is at least a quarter-mile away.
Move the telescope so the target object appears in the very
center of the field of view when you look into the eyepiece.
Now look through the finder scope. Is the object centered
in the finder scope’s field of view, i.e., on the crosshairs?
If not, hopefully it will be visible somewhere in the field of
view, so only fine adjustment of the two black nylon align-
ment screws will be needed. Otherwise you’ll have to make
coarser adjustments to the alignment screws to redirect the
aim of the finder scope.
Use the two alignment screws to center the object on the
crosshairs of the finder scope. Then look again into the main
telescope’s eyepiece and see if it is still centered there as
well. If it isn’t, repeat the entire process, making sure not to
move the main telescope while adjusting the alignment of
the finder scope.
Finder scopes can come out of alignment during trans-
port of the telescope, so check the alignment before each
observing session.
Focusing the Finder Scope
If, when looking through the finder scope, you notice that
the images appear somewhat out of focus, you will need to
refocus the finder scope for your eyes. First loosen the lock
ring located behind the objective lens cell on the body of the
finder scope (see Figure 2a). Back the lock ring off by a few
turns, for now. Refocus the finder scope on a distant object
by threading the objective lens cell in or out of the finder
scope body. Precise focusing will be achieved by focusing the
finder scope on a bright star. Once the image appears sharp,
retighten the lock ring behind the objective lens cell. The find-
er scope’s focus should not need to be adjusted again.
Terrestrial Viewing
Many people enjoy using their telescope to view objects
such as boats, birds and wildlife. The ShortTube 80 is an
excellent instrument for observing during the daylight hours.
For terrestrial applications, we recommend mounting the
ShortTube 80 on an altazimuth-style camera tripod or
telescope mount, which allow simple vertical (altitude) and
horizontal (azimuth) motions. For most telescope mounts,
you will need a 1/4”-20 adapter to couple the scope to the
mount head. Camera tripods come already equipped with a
1/4”-20 post, so no adapter is needed.
It’s best to start observing with the lower-power (25mm)
eyepiece, because it offers the wider field of view. With the
eyepiece inserted and secured in the diagonal, simply point
the telescope at the subject you want to observe and center
it on crosshairs of the finder scope (which you’ve previously
aligned with the telescope, as explained in the preceding
section). Then look into the eyepiece of the main telescope
and the subject should be in the center of the field of view. If
the view is blurry, adjust the focus with the focus wheel until
the image appears sharp.
For higher magnification, switch to the 10mm eyepiece and
readjust the focus as necessary. Remember, increasing the
magnification decreases the field of view and the image
brightness. Additional eyepieces can be purchased to obtain
a greater range of magnifications.
Astronomical Viewing
The ShortTube 80 excels for astronomical observation. Its
unobstructed 80mm aperture and short 400mm focal length
(f/5) provide bright, expansive views of star fields and celes-
tial objects residing within our solar system and beyond.
The ShortTube 80 can show much more than what is visible
on Earth during the day. Once the Sun sets, there are literally
thousands of objects in the night sky that can be inspected
more closely. For astronomical usage, we recommend a 90°
star diagonal instead of the 45° correct-image diagonal that
comes with the telescope. The correct-image diagonal is
designed for daytime use, and will cause some degradation
of image quality when used for astronomy. Also, the viewing
angle provided by a 90° star diagonal is more comfortable
for looking up. When using a star diagonal, the image in the
eyepiece will appear backwards (inverted left-to-right).
For casual stargazing, an altazimuth mount mount will do
the job just fine. But an equatorial mount, is designed to
make it easier to manually “track” the motion of celestial
objects with just one slow-motion cable. Furthermore, with
an equatorial mount you can add an optional motor drive to
track the stars automatically—a great convenience.
When selecting a location for nighttime stargazing, make
it as far away from city lights as possible. Light-polluted
skies greatly reduce what can be seen with the telescope.
Also, give your eyes at least 20 minutes to dark-adapt to the
night sky. You’ll be surprised at how many more stars you
will see! Use a red flashlight to see what you’re doing at the
telescope, or to read star charts. Red light will not spoil your
dark-adapted night vision as readily as white light will.
To find celestial objects with your telescope, you first need
to become reasonably familiar with the night sky. Unless you
know how to recognize the constellation Orion, for instance,
you won’t have much luck locating the Orion Nebula. A
simple planisphere, or star wheel, can be a valuable tool for
learning the constellations and seeing which ones are vis-
ible in the sky on a given night.
A good star chart or atlas can come in handy for helping
locate interesting objects among the dizzying multitude
of stars overhead. Except for the Moon and the brighter
planets, it is pretty time-consuming and frustrating to hunt

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for objects randomly, without knowing where to look. It is
best to have specific targets in mind before you begin look-
ing through the eyepiece.
A. The Moon
The Moon, with its rocky, cratered surface, is one of the
easiest and most interesting subjects to observe with your
telescope. The myriad craters, rilles, and jagged moun-
tain formations offer endless fascination. The best time to
observe the Moon is during a partial phase, that is, when
the Moon is not full. During partial phases, shadows cast by
crater walls and mountain peaks along the border between
the dark and light portions of the lunar disk highlight the
surface relief. A full Moon is too bright and devoid of surface
shadows to yield a pleasing view. Try using a Moon filter to
dim the Moon when it is too bright; it simply threads onto the
bottom of the eyepiece.
B. The Sun
You can change your nighttime telescope into a daytime Sun
viewer by installing an optional full-aperture solar filter over
the front opening of the ShortTube 80. The primary attraction
is sunspots, which change shape, appearance, and location
daily. Sunspots are directly related to magnetic activity in the
Sun. Many observers like to make drawings of sunspots to
monitor how the Sun is changing from day to day.
Important Note: Do not look at the Sun with any optical
instrument without a professionally made solar filter, or per-
manent eye damage could result.
C. The Planets
The planets don’t stay put like stars do (planets don’t have
fixed R.A. and Dec. coordinates), so you will have to refer
to Sky Calendar at our website, www.telescope.com, or to
charts published monthly in Astronomy, Sky & Telescope,
or other astronomy references to locate them. Venus, Mars,
Jupiter, and Saturn are the brightest objects in the sky after
the Sun and the Moon. All four of these planets are not nor-
mally visible in the sky at one time, but chances are one or
two of them will be.
D. Stars
Stars will appear like twinkling points of light in the tele-
scope. Even the largest telescopes cannot magnify stars
to appear as anything more than points of light! You can,
however, enjoy the different colors of the stars and locate
many pretty double and multiple stars. The famous “Double-
Double” in the constellation Lyra and the gorgeous two-color
double star Albireo in Cygnus are favorites. Defocusing the
image of a star slightly can help bring out its color.
E. Deep-Sky Objects
Under dark skies, you can observe a number of brighter
deep-sky objects with your ShortTube 80, including gas-
eous nebulas, open and globular star clusters, and the
brighter galaxies. Most deep-sky objects are very faint, so it
is important that you find an observing site well away from
light pollution. Take plenty of time to let your eyes adjust
to the darkness. Don’t expect these objects to appear like
the photographs you see in books and magazines; most
will look like dim gray “ghosts.” (Our eyes are not sensitive
enough to see color in deep-sky objects except in few of the
brightest ones.) But as you become more experienced and
your observing skills improve, you will be able to coax out
more and more intricate details.
Calculating Magnification
(Power)
It is desirable to have a range of eyepieces of different focal
lengths, to allow viewing over a range of magnifications. To
calculate the magnification, or power, of a telescope, simply
divide the focal length of the telescope by the focal length of
the eyepiece:
Magnification = Telescope F.L. ÷ Eyepiece F.L.
For example, the ShortTube 80, which has a focal length of
400mm, used in combination with the supplied 25mm Sirius
Plössl eyepiece, yields a power of
400 ÷ 25 = 16x.
Every telescope has a useful limit of power of about 45x-60x
per inch of aperture, which is 140x-180x for the ShortTube
80. Claims of higher power by some telescope manufactur-
ers are a misleading advertising gimmick and should be
dismissed. Keep in mind that at higher powers, an image will
always be dimmer and less sharp (this is a fundamental law
of optics). The steadiness of the air (the “seeing”) can also
limit how much magnification an image can tolerate.
Always start viewing with your lowest-power (longest focal
length) eyepiece in the telescope. After you have located
and looked at the object with it, you can try switching to a
higher-power eyepiece, like the supplied 10mm Sirius Plössl
eyepiece, to ferret out more detail. If the image you see is not
crisp and steady, reduce the magnification by switching to a
longer-focal-length eyepiece. As a general rule, a small but
well-resolved image will show more detail and provide a more
enjoyable view than a dim and fuzzy, overmagnified image.
Photography with the ShortTube 80
With an optional camera adapter, the ShortTube 80
becomes a 400mm f/5 telephoto lens for a single-lens reflex
camera. For long-distance terrestrial or astronomical pho-
tography, you need only a T-ring for your particular camera
model. The T-ring attaches to your particular camera model
Figure 3. The ShortTube 80 with 35mm SLR camera attached.

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and threads onto the ShortTube’s focuser drawtube, cou-
pling the camera body to the telescope (Figure 3).
For closer-range (less than 1/4-mile) terrestrial photography,
you need both a T-ring for your camera and a T-adapter
(#5264), which provides the extra focus travel needed.
Remove the nosepiece from the camera adapter; the body
of the adapter will not be needed here. Connect the T-ring
to your camera body (remove any camera lenses first), and
connect the nosepiece of the camera adapter to the T-ring.
Now, insert the entire assembly into the focuser’s drawtube
(remove the eyepiece and diagonal), and secure with the
thumbscrew on the drawtube. Be sure to tighten the thumb-
screw, or your camera could fall to the ground!
Use the camera’s viewfinder to frame the picture. Use the
telescope’s focuser to focus the image. Tighten the focus
lock thumbscrew on the telescope’s focuser to make sure
the camera does not slip out of focus.
You may want to consider using a remote shutter release
instead of the shutter release on the camera. Touching the
camera can vibrate the system and blur the resulting photo-
graphic image. Also, be sure to use a solid tripod.
Care & Maintenance
Give your telescope reasonable care and it will last a life-
time. Store it indoors or in a dry garage. Do not leave the
telescope outside except when using it. The optical tube is
aluminum and has a smooth painted surface that should
resist scratches and smudges. If a scratch does appear
on the tube, it will not harm the telescope. If you wish, you
can apply some white auto touch-up paint to the scratch.
Smudges on the tube can be wiped off with standard house-
hold cleaners such as Windex or Formula 409.
Any quality optical lens tissue and cleaning fluid specifically
designed for multi-coated optics can be used to clean the
telescope’s objective lens as well as the lenses of the eye-
pieces and finder scope. Never use regular glass cleaner or
cleaning fluid designed for eyeglasses. Before cleaning with
fluid and tissue, however, blow any loose particles off the
lens with a blower bulb or compressed air, or lightly brush
the lens with a soft camel hair brush. Apply some cleaning
fluid to a tissue, never directly on the optics. Wipe the lens
gently in a circular motion, then remove any excess fluid
with a fresh lens tissue. Oily fingerprints and smudges may
be removed using this method. Use caution; rubbing too
hard may scratch the lens! On larger lenses, clean only a
small area at a time, using a fresh lens tissue on each area.
Never reuse tissues.
Specifications
Objective lens: 80mm glass achromat, fully coated
Focal length: 400mm
Focal ratio: f/5
Optical tube length: 15"
Weight of optical tube assembly: 3 lbs., 7 oz.
Mounting provision: 1/4"-20 threaded receptacle
Finder scope: 6x magnification, 26mm aperture, correct-
image, achromatic, crosshairs
Eyepieces: 25mm (16x) and 10mm (40x) Sirius Plössl,
1.25" barrel diameter, fully coated
Diagonal: 45° correct-image, 1.25" barrel diameter

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One-Year Limited Warranty
The Orion ShortTube™ 80mm Refractor is warranted against defects in materials or work-
manship for a period of one year from the date of purchase. This warranty is for the benefit of
the original retail purchaser only. During this warranty period Orion Telescopes & Binoculars
will repair or replace, at Orion’s option, any warranted instrument that proves to be defective,
provided it is returned postage paid to: Orion Warranty Repair, 89 Hangar Way, Watsonville,
CA 95076. Proof of purchase (such as a copy of the original receipt) is required.
This warranty does not apply if, in Orion’s judgment, the instrument has been abused, mishan-
dled, or modified, nor does it apply to normal wear and tear. This warranty gives you specific legal
rights, and you may also have other rights, which vary from state to state. For further warranty
service information, contact: Customer Service Department, Orion Telescopes & Binoculars, P. O.
Box 1815, Santa Cruz, CA 95061; [phone].